From: Minep <lunaixsky@qq.com>
Date: Sun, 23 Jul 2023 13:35:18 +0000 (+0100)
Subject: refactor: Optimize the signal context overhead
X-Git-Url: https://scm.lunaixsky.com/lunaix-os.git/commitdiff_plain/04ee277abd77fc51c5ab02ee58790a859607ea24?hp=946c3fdd31300074cc78841795bd47af908ddddb

refactor: Optimize the signal context overhead
refactor: remove kernel memory overhead for saving x87 context by saving it into user stack
---

diff --git a/lunaix-os/.prettierignore b/lunaix-os/.prettierignore
new file mode 100644
index 0000000..b2eb281
--- /dev/null
+++ b/lunaix-os/.prettierignore
@@ -0,0 +1 @@
+*.S.inc
\ No newline at end of file
diff --git a/lunaix-os/includes/arch/x86/i386_asm.h b/lunaix-os/includes/arch/x86/i386_asm.h
index 5fec5b3..b6e8d05 100644
--- a/lunaix-os/includes/arch/x86/i386_asm.h
+++ b/lunaix-os/includes/arch/x86/i386_asm.h
@@ -7,4 +7,6 @@
 #define UDATA_SEG 0x23
 #define TSS_SEG 0x28
 
+#define stack_alignment 0xfffffff0
+
 #endif /* __LUNAIX_I386_ASM_H */
diff --git a/lunaix-os/includes/arch/x86/interrupt.S.inc b/lunaix-os/includes/arch/x86/interrupt.S.inc
new file mode 100644
index 0000000..2d95fac
--- /dev/null
+++ b/lunaix-os/includes/arch/x86/interrupt.S.inc
@@ -0,0 +1,90 @@
+
+#define regsize 4
+
+/* stack layout: saved interrupt context */
+    .struct 0
+idepth:
+    .struct idepth + regsize
+ieax:
+    .struct ieax + regsize
+iebx:
+    .struct iebx + regsize
+iecx:
+    .struct iecx + regsize
+iedx:
+    .struct iedx + regsize
+iedi:
+    .struct iedi + regsize
+iebp:
+    .struct iebp + regsize
+iesi:
+    .struct iesi + regsize
+ids:
+    .struct ids + regsize
+ies:
+    .struct ies + regsize
+ifs:
+    .struct ifs + regsize
+igs:
+    .struct igs + regsize
+iexecp:
+iesp:
+    .struct iesp + regsize
+isave_prev:
+    .struct isave_prev + regsize
+ivec:
+    .struct ivec + regsize
+iecode:
+    .struct iecode + regsize
+ieip:
+    .struct ieip + regsize
+ics:
+    .struct ics + regsize
+ieflags:
+    .struct ieflags + regsize
+iuesp:
+    .struct iuesp + regsize
+iuss:
+
+
+/* stack layout: execution (flow-control) state context */
+    .struct 0
+exsave_prev:
+    .struct exsave_prev + regsize
+exvec:
+    .struct exvec + regsize
+execode:
+    .struct execode + regsize
+exeip:
+    .struct exeip + regsize
+excs:
+    .struct excs + regsize
+exeflags:
+    .struct exeflags + regsize
+exuesp:
+    .struct exuesp + regsize
+exuss:
+
+/* struct layout: critical section of struct proc_info */
+    .struct 0
+proc_pid:
+    .struct proc_pid + regsize
+proc_parent:
+    .struct proc_parent + regsize
+proc_intr_ctx:
+    .struct proc_intr_ctx + regsize
+proc_ustack_top:
+    .struct proc_ustack_top + regsize
+proc_page_table:
+    .struct proc_page_table + regsize
+proc_fxstate:
+
+/* struct layout: proc_sig */
+    .struct 0
+psig_signum:
+    .struct psig_signum + regsize
+psig_sigact:
+    .struct psig_sigact + regsize
+psig_sighand:
+    .struct psig_sighand + regsize
+psig_saved_ictx:
\ No newline at end of file
diff --git a/lunaix-os/includes/lunaix/common.h b/lunaix-os/includes/lunaix/common.h
index c9ef9e4..ac0b4d4 100644
--- a/lunaix-os/includes/lunaix/common.h
+++ b/lunaix-os/includes/lunaix/common.h
@@ -13,6 +13,7 @@
 #define KSTACK_SIZE MEM_1MB
 #define KSTACK_START (USER_START - KSTACK_SIZE)
 #define KSTACK_TOP ((USER_START - 1) & ~0xf)
+#define within_kstack(addr) (KSTACK_START <= (addr) && (addr) <= KSTACK_TOP)
 
 #define KERNEL_MM_BASE 0xC0000000
 
diff --git a/lunaix-os/includes/lunaix/process.h b/lunaix-os/includes/lunaix/process.h
index bb55f02..7d385a4 100644
--- a/lunaix-os/includes/lunaix/process.h
+++ b/lunaix-os/includes/lunaix/process.h
@@ -41,18 +41,12 @@
 #define PS_GrBP (PS_PAUSED | PS_BLOCKED)
 #define PS_GrDT (PS_TERMNAT | PS_DESTROY)
 
-#define PROC_TERMINATED(state) ((state)&PS_GrDT)
-#define PROC_HANGED(state) ((state)&PS_BLOCKED)
-#define PROC_RUNNABLE(state) ((state)&PS_PAUSED)
+#define proc_terminated(proc) (((proc)->state) & PS_GrDT)
+#define proc_hanged(proc) (((proc)->state) & PS_BLOCKED)
+#define proc_runnable(proc) (((proc)->state) & PS_PAUSED)
 
 #define PROC_FINPAUSE 1
 
-struct proc_sigstate
-{
-    isr_param proc_regs;
-    char fxstate[512] __attribute__((aligned(16)));
-};
-
 struct sigact
 {
     struct sigact* prev;
@@ -75,7 +69,7 @@ struct proc_sig
     int sig_num;
     void* sigact;
     void* sighand;
-    struct proc_sigstate prev_context;
+    isr_param* saved_ictx;
 } __attribute__((packed));
 
 struct proc_info
@@ -93,7 +87,6 @@ struct proc_info
     isr_param* intr_ctx;      // offset = 8
     ptr_t ustack_top;         // offset = 84 -> 56 -> 60 -> 12
     ptr_t page_table;         // offset = 88 -> 60 -> 64 -> 16
-    void* fxstate;            // offset = 92 -> 64 -> 68 -> 20
 
     /* ---- critical section end ---- */
 
diff --git a/lunaix-os/kernel/asm/x86/interrupt.S b/lunaix-os/kernel/asm/x86/interrupt.S
index 3007d45..80dee1a 100644
--- a/lunaix-os/kernel/asm/x86/interrupt.S
+++ b/lunaix-os/kernel/asm/x86/interrupt.S
@@ -3,6 +3,8 @@
 #include <arch/x86/i386_asm.h>
 #include <arch/x86/tss.h>
 #include <lunaix/syscall.h>
+#include <arch/x86/interrupt.S.inc>
+
 #define __ASM_INTR_DIAGNOSIS
 
 #ifdef __ASM_INTR_DIAGNOSIS
@@ -30,85 +32,6 @@
 
 */
 
-#define regsize 4
-
-/* stack layout: saved interrupt context */
-    .struct 0
-idepth:
-    .struct idepth + regsize
-ieax:
-    .struct ieax + regsize
-iebx:
-    .struct iebx + regsize
-iecx:
-    .struct iecx + regsize
-iedx:
-    .struct iedx + regsize
-iedi:
-    .struct iedi + regsize
-iebp:
-    .struct iebp + regsize
-iesi:
-    .struct iesi + regsize
-ids:
-    .struct ids + regsize
-ies:
-    .struct ies + regsize
-ifs:
-    .struct ifs + regsize
-igs:
-    .struct igs + regsize
-iesp:
-    .struct iesp + regsize
-isave_prev:
-    .struct isave_prev + regsize
-ivec:
-    .struct ivec + regsize
-iecode:
-    .struct iecode + regsize
-ieip:
-    .struct ieip + regsize
-ics:
-    .struct ics + regsize
-ieflags:
-    .struct ieflags + regsize
-iuesp:
-    .struct iuesp + regsize
-iuss:
-
-
-/* stack layout: execution (flow-control) state context */
-    .struct 0
-exsave_prev:
-    .struct exsave_prev + regsize
-exvec:
-    .struct exvec + regsize
-execode:
-    .struct execode + regsize
-exeip:
-    .struct exeip + regsize
-excs:
-    .struct excs + regsize
-exeflags:
-    .struct exeflags + regsize
-exuesp:
-    .struct exuesp + regsize
-exuss:
-
-/* struct layout: critical section of struct proc_info */
-    .struct 0
-proc_pid:
-    .struct proc_pid + regsize
-proc_parent:
-    .struct proc_parent + regsize
-proc_intr_ctx:
-    .struct proc_intr_ctx + regsize
-proc_ustack_top:
-    .struct proc_ustack_top + regsize
-proc_page_table:
-    .struct proc_page_table + regsize
-proc_fxstate:
-
 .section .text
     .global interrupt_wrapper
     interrupt_wrapper:
@@ -168,7 +91,8 @@ proc_fxstate:
         andl $0x3, %eax          /* 判断 RPL */
         jz 1f
 
-        movw $KDATA_SEG, %ax    /* 如果从用户模式转来，则切换至内核数据段 */
+    /* crossing the user/kernel boundary */
+        movw $KDATA_SEG, %ax
         movw %ax, %gs
         movw %ax, %fs
         movw %ax, %ds
@@ -176,18 +100,21 @@ proc_fxstate:
 
         movl __current, %eax
 
-        # FIXME: Save x87 context to user stack, rather than kernel's memory.
-        # 保存x87FPU的状态
-        movl proc_fxstate(%eax), %ebx
-        fxsave (%ebx)
-
         # 保存用户栈顶指针。因为我们允许同级中断的产生，所以需要该手段跟踪用户栈的地址。
         movl iuesp(%esp), %ebx     # 取出esp
         movl %ebx, proc_ustack_top(%eax)     # 存入__current->ustack_top
 
+        # Save x87 context to user stack, rather than kernel's memory.
+        # XXX: what will happen if we triggered a page fault during fxsave?
+        movl iuesp(%esp), %eax
+        andl $stack_alignment, %eax 
+        subl $512, %eax
+        fxsave (%eax)
+
+    /* kernel space same-level switch */
     1:
         movl %esp, %eax
-        andl $0xfffffff0, %esp
+        andl $stack_alignment, %esp
         subl $16, %esp
         movl %eax, (%esp)
 
@@ -205,12 +132,19 @@ proc_fxstate:
         movl exeip(%eax), %eax
         movl %eax, (debug_resv + 4) # eip
 #endif
-        movl __current, %eax
-        movl proc_fxstate(%eax), %eax
+        // movl __current, %eax
+        // movl proc_fxstate(%eax), %eax
         
-        test %eax, %eax     # do we have stored x87 context?
+        // test %eax, %eax     # do we have stored x87 context?
+
+        movl ics(%esp), %eax
+        andl $3, %eax
         jz 1f 
-        fxrstor (%eax) 
+
+        movl iuesp(%esp), %eax
+        andl $stack_alignment, %eax 
+        subl $512, %eax
+        fxrstor (%eax)
 
 1:
         popl %eax   # discard isr_param::depth
@@ -276,16 +210,16 @@ proc_fxstate:
         # 我们已经处在了新的地址空间，为了避免影响其先前的栈布局
         # 需要使用一个临时的栈空间
         movl $tmp_stack, %esp
-        
-        # 更新 tss
-        movl proc_intr_ctx(%ebx), %eax      # proc->intr_ctx
-        movl iesp(%eax), %eax      # intr_ctx->esp
-        movl %eax, (tss_esp0_off + _tss)
 
         call signal_dispatch    # kernel/signal.c
 
         test %eax, %eax         # do we have signal to handle?
         jz 1f
+
+        # 更新 tss
+        movl proc_intr_ctx(%ebx), %ecx      # __current->intr_ctx
+        movl %ecx, (tss_esp0_off + _tss)
+
         jmp handle_signal
     1:
         movl proc_intr_ctx(%ebx), %eax
@@ -296,16 +230,16 @@ proc_fxstate:
         # 注意1：任何对proc_sig的布局改动，都须及时的保证这里的一致性！
         # 注意2：handle_signal在调用之前，须确保proc_sig已经写入用户栈！
         # arg1 in %eax: addr of proc_sig structure in user stack
-        leal 12(%eax), %ebx      # %ebx = &proc_sig->prev_context
+        movl psig_saved_ictx(%eax), %ebx      # %ebx = &proc_sig->saved_ictx
 
-        pushl $UDATA_SEG        # proc_sig->prev_context.proc_regs.ss
+        pushl $UDATA_SEG
         pushl %eax              # esp
 
-        movl 48(%ebx), %ebx
-        pushl 68(%ebx)          # proc_sig->prev_context.proc_regs.execp->eflags
+        movl iexecp(%ebx), %ebx
+        pushl exeflags(%ebx)          # proc_sig->saved_ictx->execp->eflags
         
         pushl $UCODE_SEG        # cs
-        pushl 4(%eax)           # %eip = proc_sig->sigact
+        pushl psig_sigact(%eax)           # %eip = proc_sig->sigact
 
         movw $UDATA_SEG, %cx    # switch data seg to user mode
         movw %cx, %es
diff --git a/lunaix-os/kernel/k_init.c b/lunaix-os/kernel/k_init.c
index 8c40b6b..2dc39e6 100644
--- a/lunaix-os/kernel/k_init.c
+++ b/lunaix-os/kernel/k_init.c
@@ -165,11 +165,6 @@ spawn_proc0()
 
     proc0->intr_ctx = isrp;
 
-    // 加载x87默认配置
-    asm volatile("fninit\n"
-                 "fxsave (%%eax)" ::"a"(proc0->fxstate)
-                 : "memory");
-
     // 向调度器注册进程。
     commit_process(proc0);
 
diff --git a/lunaix-os/kernel/process/process.c b/lunaix-os/kernel/process/process.c
index 4e8fa0a..63fc7ad 100644
--- a/lunaix-os/kernel/process/process.c
+++ b/lunaix-os/kernel/process/process.c
@@ -211,8 +211,6 @@ dup_proc()
     pcb->intr_ctx = __current->intr_ctx;
     pcb->parent = __current;
 
-    memcpy(pcb->fxstate, __current->fxstate, 512);
-
     if (__current->cwd) {
         pcb->cwd = __current->cwd;
         vfs_ref_dnode(pcb->cwd);
diff --git a/lunaix-os/kernel/process/sched.c b/lunaix-os/kernel/process/sched.c
index 1587848..acf04b7 100644
--- a/lunaix-os/kernel/process/sched.c
+++ b/lunaix-os/kernel/process/sched.c
@@ -142,7 +142,7 @@ check_sleepers()
     time_t now = clock_systime();
     llist_for_each(pos, n, &leader->sleep.sleepers, sleep.sleepers)
     {
-        if (PROC_TERMINATED(pos->state)) {
+        if (proc_terminated(pos)) {
             goto del;
         }
 
@@ -343,8 +343,6 @@ alloc_process()
     proc->created = clock_systime();
     proc->pgid = proc->pid;
     proc->fdtable = vzalloc(sizeof(struct v_fdtable));
-    proc->fxstate =
-      vzalloc_dma(512); // FXSAVE需要十六位对齐地址，使用DMA块（128位对齐）
 
     llist_init_head(&proc->mm.regions);
     llist_init_head(&proc->tasks);
@@ -415,7 +413,6 @@ destroy_process(pid_t pid)
     }
 
     vfree(proc->fdtable);
-    vfree_dma(proc->fxstate);
 
     vmm_mount_pd(VMS_MOUNT_1, proc->page_table);
 
@@ -466,5 +463,5 @@ orphaned_proc(pid_t pid)
 
     // 如果其父进程的状态是terminated 或 destroy中的一种
     // 或者其父进程是在该进程之后创建的，那么该进程为孤儿进程
-    return PROC_TERMINATED(parent->state) || parent->created > proc->created;
+    return proc_terminated(parent) || parent->created > proc->created;
 }
\ No newline at end of file
diff --git a/lunaix-os/kernel/process/signal.c b/lunaix-os/kernel/process/signal.c
index 15c650d..d00e757 100644
--- a/lunaix-os/kernel/process/signal.c
+++ b/lunaix-os/kernel/process/signal.c
@@ -4,6 +4,9 @@
 #include <lunaix/spike.h>
 #include <lunaix/status.h>
 #include <lunaix/syscall.h>
+#include <lunaix/syslog.h>
+
+LOG_MODULE("SIG")
 
 #include <klibc/string.h>
 
@@ -11,6 +14,13 @@ extern struct scheduler sched_ctx; /* kernel/sched.c */
 
 #define UNMASKABLE (sigset(SIGKILL) | sigset(SIGTERM))
 #define TERMSIG (sigset(SIGSEGV) | sigset(SIGINT) | UNMASKABLE)
+#define CORE (sigset(SIGSEGV))
+
+static inline void
+signal_terminate(int errcode)
+{
+    terminate_proc(errcode | PEXITSIG);
+}
 
 // Referenced in kernel/asm/x86/interrupt.S
 void*
@@ -38,7 +48,7 @@ signal_dispatch()
 
     if (!action->sa_actor) {
         if (sigset_test(TERMSIG, sig_selected)) {
-            terminate_proc(sig_selected | PEXITSIG);
+            signal_terminate(sig_selected);
             schedule();
             // never return
         }
@@ -55,35 +65,11 @@ signal_dispatch()
     struct proc_sig* sigframe =
       (struct proc_sig*)((ustack - sizeof(struct proc_sig)) & ~0xf);
 
-    /*
-        这是一个相当恶心的坑。
-        问题是出在原本的sigframe->prev_context = __current->intr_ctx的上面
-        这个语句会被gcc在编译时，用更加高效的 rep movsl 来代替。
-
-        由于我们采用按需分页，所以在很多情况下，用户栈实际被分配的空间不允许我们进行完整的
-        注入，而需要走page fault handler进行动态分页。
-
-        竞态条件就出现在这里！
-
-        假若我们的__current->intr_ctx注入了一半，然后产生page-fault中断，
-        那么这就会导致我们的__current->intr_ctx被这个page-fault中断导致的
-        上下文信息覆盖。那么当page-fault handler成功分配了一个页，返回，
-        拷贝也就得以进行。遗憾的是，只不过这次拷贝的内容和前面的拷贝是没有任何的关系
-        （因为此时的intr_ctx已经不是之前的intr_ctx了！）
-        而这就会导致我们保存在信号上下文中的进程上下文信息不完整，从而在soft_iret时
-        触发#GP。
-
-        解决办法就是先吧intr_ctx拷贝到一个静态分配的区域里，然后再注入到用户栈。
-    */
-    static volatile struct proc_sigstate __temp_save;
-    __temp_save.proc_regs = *__current->intr_ctx;
-    memcpy(__temp_save.fxstate, __current->fxstate, 512);
-
     sigframe->sig_num = sig_selected;
-
     sigframe->sigact = action->sa_actor;
     sigframe->sighand = action->sa_handler;
-    sigframe->prev_context = __temp_save;
+
+    sigframe->saved_ictx = __current->intr_ctx;
 
     action->prev = prev_working;
     psig->inprogress = action;
@@ -135,7 +121,7 @@ send_grp:
     }
 
 send_single:
-    if (PROC_TERMINATED(proc->state)) {
+    if (proc_terminated(proc)) {
         __current->k_status = EINVAL;
         return -1;
     }
@@ -148,9 +134,7 @@ send_single:
 
 __DEFINE_LXSYSCALL1(int, sigreturn, struct proc_sig, *sig_ctx)
 {
-    memcpy(__current->fxstate, sig_ctx->prev_context.fxstate, 512);
-    // FIXME: Interrupt context is exposed to user space!
-    *__current->intr_ctx = sig_ctx->prev_context.proc_regs;
+    __current->intr_ctx = sig_ctx->saved_ictx;
 
     struct sigact* current = __current->sigctx.inprogress;
     if (current) {
@@ -160,6 +144,24 @@ __DEFINE_LXSYSCALL1(int, sigreturn, struct proc_sig, *sig_ctx)
         __current->sigctx.inprogress = NULL;
     }
 
+    if (proc_terminated(__current)) {
+        __current->exit_code |= PEXITSIG;
+    } else if (sigset_test(CORE, sig_ctx->sig_num)) {
+        signal_terminate(sig_ctx->sig_num);
+    }
+
+    ptr_t ictx = (ptr_t)__current->intr_ctx;
+
+    /*
+        Ensure our restored context is within kernel stack
+
+        This prevent user to forge their own context such that arbitrary code
+       can be executed as supervisor level
+    */
+    if (!within_kstack(ictx)) {
+        signal_terminate(SIGSEGV);
+    }
+
     schedule();
 
     // never reach!
diff --git a/lunaix-os/usr/init/init.c b/lunaix-os/usr/init/init.c
index 0ed0d0b..b3eaae5 100644
--- a/lunaix-os/usr/init/init.c
+++ b/lunaix-os/usr/init/init.c
@@ -35,7 +35,7 @@ main(int argc, const char** argv)
 
     waitpid(pid, &err, 0);
 
-    if (err) {
+    if (WEXITSTATUS(err)) {
         printf("shell exit abnormally (%d)", err);
     }
 
diff --git a/lunaix-os/usr/libc/arch/i386/crt0.S b/lunaix-os/usr/libc/arch/i386/crt0.S
index 28aa6ba..eec9ee9 100644
--- a/lunaix-os/usr/libc/arch/i386/crt0.S
+++ b/lunaix-os/usr/libc/arch/i386/crt0.S
@@ -10,6 +10,7 @@
     .global _start
     _start:        
         xorl %eax, %eax
+        fninit
         call main
         
     1:
diff --git a/lunaix-os/usr/signal_demo/signal_demo.c b/lunaix-os/usr/signal_demo/signal_demo.c
index b20f4ad..352d0de 100644
--- a/lunaix-os/usr/signal_demo/signal_demo.c
+++ b/lunaix-os/usr/signal_demo/signal_demo.c
@@ -24,7 +24,7 @@ sigalrm_handler(int signum)
     printf("I, pid %d, have received an alarm!\n", pid);
 }
 
-void
+int
 main()
 {
     signal(SIGCHLD, sigchild_handler);
@@ -72,4 +72,6 @@ main()
     }
 
     printf("done\n");
+
+    return 0;
 }
\ No newline at end of file